Mysterious TCP/IP Issue

Randomly throughout the day, my Exchange server will be unreachable through the network. I started thinking it was an Exchange problem because we were getting multiple error messages in the logs. After fighting this for weeks I've narrowed it down to something that I think is TCP/IP related. The error messages were occuring because the server was cut off from everything else. When the server loses its connection I can restore it by either disabling and enabling the NIC or by unplugging the network cable for a few seconds. I thought it might be the NIC so I bought a new 3com card but still the same problem. Next I followed Microsofts directions and uninstalled all networking services, uninstalled TCP/IP, deleted all the registry keys, then reinstalled everything. No dice. There is no pattern to when it goes down, only the fact that it's in groups. It will go down 10 times in 30 minutes then be a-ok for 18 hours, then it will go down 4 times, then be up for 11 hours. I had an "expert" come in and look at it but he found nothing either. He thought it might be VPN or RRAS so I disabled both but that didn't help.

The server is a compaq dual p3 800 running 2ksp3. The only thing on it besides Exchange is Symantec Corporate AV 8.0. There were a few websites, but we moved them to another server when this started happening. Now the only available site is the OWA.

What gives? Does this machine need a complete rebuild of windows? Thanks for any help.

What is it connected to? A 10/100 switch? What kind of switch? Is it hard-coded to connect the server at 100/full-duplex, or set to autosense? Are there any port errors on the switch port? It could be a duplex mismatch problem.
Are both cards 3Com and the switch Cisco?
Here's some good background information on this issue.http://www.cisco.com/warp/customer/473/46.html

What makes you believe it is TCP/IP related? Does this server have manually set IP address information? Is there a DHCP server that might not have that server's IP address excluded in its scope?

The server is connected to a generic linksys switch that is set to autosense. This is the only machine on that switch that is having the problem. The switch is soon to be replaced with something good, probably a Cisco 2950. I have not noticed any port errors on the linksys, but I never thought to pay too much attention there. I will now, though.

The LAN IP address is set manually to work with our one-to-one NAT. The IP address is not in the available pool for our only DHCP server.

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Maybe this is too obvious but I noticed sometimes this could be overseen..:)
I presume you have checked in the properties of the nick that "allow the computer to switch this device off to save energy" is set to off ?

Yeah, I did some searching in the Google Groups and found alot of information about the ACPI settings. The new cards default setting for power management is disabled, so I don't think it's the card. Next time I can reboot I'm going to check to see if the ACPI bios is turned on. The only problem with that is there is a possibility that turning it off means a complete reinstall of windows.

Finally, 13 years later, my boss let me buy a good switch. I got a 3com 3900 and set both the NIC and the switch to 100-FullDuplex. For the past 2 days the server has been running like a Kennedy at Mardi Gras.

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